The present invention generally relates to a piezoelectric vibrator comprising a generally parallelogrammical piezoelectric vibrating element including a vibrateable substrate made of a constant elastic metal, i.e., a metallic material having a constant modulus of elasticity, and, more particularly, to the support of the piezoelectric vibrating element by a retaining means through a pair of connecting elements.
The piezoelectric vibrator of the type referred to above is well known in the art. In this known piezoelectric vibrator, in order for the vibration induced in the peizoelectric vibrating element not to be suppressed, or otherwise adversely affected, by the connecting elements used to connect it to the retaining means, the width of each of the connecting elements as measured in a direction parallel to the lengthwise direction of one or two pairs of sides of the shape of the piezoelectric vibrating element, for example, the lengthwise direction of each of the paired shorter sides in the case where the piezoelectric vibrating element is of rectangular shape, is customarily selected to be of a small value as compared with the length of each of such paired shorter sides. It is generally recognized that the smaller the width of each connecting element, the better.
However, it has been found that the prior art piezoelectric vibrator wherein the width of each connecting element is smaller than one tenth of the length of each shorter side of the piezoelectric vibrating element tends to produce, as shown in FIG. 5 of the accompanying drawings, not only a requisite expansion vibration A propagating in a direction parallel to the respective shorter side of the piezoelectric element, but also such unwanted vibrations as flexure vibration B propagating in a direction lengthwise of the shorter side, an expansion vibration C propagating in a direction lengthwise of the longer sides and Lamb wave D, with the result that the vibrating characteristic thereof is lowered.
In view of the foregoing, the piezoelectric vibrator is fabricated into a bimorph structure comprising, as shown in FIG. 6 of the accompanying drawings, a vibrateable substrate 01 having its opposite surfaces provided with a respective thin film 02 of piezoelectric material and a respective exciting electrode layer 03 overlaid on the associated piezoelectric thin film 02, the exciting electrode layers 03 being adapted to be connected to a source 04 of drive current in parallel, but reverse-biased relation to each other so that the applied voltage can cause the piezoelectric thin films 02 to flex in the opposite directions with respect to each other. In this way, the flexure vibration can be counteracted thereby to minimize the generation of the unwanted vibrations.
Fabrication of the piezoelectric vibrator so as to have a bimorph structure has been found to result in an increased amount of material required as well as an increased number of manufacturing process steps which in turn often constitutes a cause of deviation in design dimension from one piezoelectric vibrator to another.